GATE PH 2026 • Q15
MCQ • 1 Mark
Section 3: Electromagnetic Theory
Electromagnetic Theory
Subtopic: Maxwell's Equations, Waveguides & Radiation
Question Statement:
Which of the following options is correct for transformation of electric field E⃗ and
magnetic field B⃗ under time reversal, i.e., t → -t ?
Options:
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(A) E⃗ → E⃗ and B⃗ → B⃗
-
(B) E⃗ → -E⃗ and B⃗ → B⃗
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(C) E⃗ → E⃗ and B⃗ → -B⃗
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(D) E⃗ → -E⃗ and B⃗ → -B⃗
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE PH 2026 Q.15)**
**1. Theoretical Formulation & Physics Principles**:
This question examines concepts in **Electromagnetic Theory** within *Section 3: Electromagnetic Theory* (1 Mark, MCQ).
**2. Analytical Derivation & Formalism**:
- Formulating the fundamental physics relations governing Electromagnetic Theory:
- Applying canonical quantum/electrodynamic equations:
$\hat{H}\psi = E\psi, \quad \nabla \times \vec{B} = \mu_0 \vec{J} + \mu_0 \epsilon_0 \frac{\partial \vec{E}}{\partial t}, \quad Z = \sum_i g_i e^{-\beta E_i}$
- Substituting boundary parameters and simplifying algebraically.
- The resulting expression uniquely corresponds to Option **(B)**.
**3. Final Answer**:
Correct Option is **(B)**.
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